A ray of hope for small communities—the economical ANBR STP system

Ecotech has been a staunch advocate of the classic Extended Aeration Activated Sludge (EAAS) technology for micro, mini, and small STPs in commercial and residential complexes. SBR (Sequencing Batch Reactor) and MBBR (Moving Bed Biofilm Reactor) are fine technologies, but appropriate only in large scale municipal STPs of 10 MLD and above. In such STPs, effluent flow characteristics are more uniform and favourable. Further, the scale of these plants allows for the use of the necessary mechanical decanter for SBR, and a primary sedimentation stage for MBBR.

For long we have been hesitant to engage with small communities for their STP requirements, since the EAAS system is not economically viable for communities with under 150 flats (<100KLD). The cost of operation & maintenance of such small STPs would be a killer, making the STP dysfunctional in double quick time. This messy cesspool would rapidly turn into a breeding ground for mosquitoes and other disease vectors. We wanted no part of this to become a blot on our escutcheon.

Recently however, the Govt. of Karnataka mandated that all apartments with 50 flats or more must perforce set up an STP. And this got us to rethink our policy on such micro STPs. There are several sharks, charlatans, voodoo practitioners, shamans, and of course the usual suspects—ignorant plumbing consultants, who will swoop down upon these innocent communities like vultures of prey and suck the lifeblood out of honest citizens.

As qualified and trained chemical and environmental engineers of high integrity, we took it upon ourselves to rise to the challenge to help this hapless lot. And thus was born the Anaerobic Baffled Reactor (ANBR) system of STP for small communities. Not exactly an invention, but an improved version of a seminal work in this direction by Herr Ludwig Sasse of Germany in the '90s, adapted by us for Indian metro cities. We had to bring to bear all our chemical engineering knowledge in conjunction with our environmental engineering background to fine tune the design and engineering of the ANBR system. The goal was to make it practically operator free with a bare minimum of equipment and maintenance.

As an aside—Herr Sasse’s technical brilliance is matched only by his outlandish, peculiar sense of Teutonic humour—more on this in the footnote.

We recently commissioned our first 60 KLD ANBR STP for a residential complex in Bangalore. After initial hiccups, caused not by our design, but by improper implementation of our instructions, the STP has settled down well. It is yielding treated water of excellent quality which is now recycled and reused for toilet flush. Even the lingering suspicion that long periods of stagnation of anaerobically treated sewage may result in turbid, blackish, and odorous product was proved to be ill-founded. The treated water retained its initial character even after 21 hours of standing, well into the next day. See image below.

From left to right:

(1) After ANBR, before sand filter

(2) After carbon filter

(3) After chlorination

Crystal clear, colourless, and odourless! What more can one ask for?

FOOTNOTE : Pearls of Wisdom from Herr Ludwig Sasse’s Handbook

Wastewater engineers are probably the only ones who love handling wastewater

It is the duty of the technician to deliver an appropriate design which will be realised with an appropriate technology (This is what we have been preaching all along)

Low-maintenance does not mean NO-maintenance

The first economic question is "Why", only the second question is "How much" (Well said!)

A wastewater treatment plant is NOT just another pair of shoes (We are still trying to figure this one out)